The invention relates to a heat management system for an internal combustion engine.
The heat management of the coolant circuits of an internal combustion engine has a great influence on fuel consumption. In particular, operation of the engine at optimum temperatures, and efficient operation of consumers, such as for example a vehicle interior heater, but also rapid heating of the engine and transmission oil, assist in saving fuel.
DE 10 2005 035 121 A1 presents a cooling system which makes it possible for a valve arranged in the heating circuit to throttle or entirely stop the throughflow to the heater as required. It is however a disadvantage here that an additional component, namely the valve, must be installed.
It is an object of the invention to provide a simple and inexpensive heat management system by means of which the individual coolant circuits of the internal combustion engine can be controlled in a flexible manner.
This is achieved according to the invention in the case of a heat management system for an internal combustion engine, having an engine cooling circuit, a main cooler circuit with a main cooler, a heating circuit with a heating heat exchanger, a coolant pump which moves coolant through the circuits, and a rotary slide valve with at least one switched and at least one non-switched inlet, wherein the heating return line issues into a switched inlet of the rotary slide valve.
In very general terms, the rotary slide valve offers the advantage of a temperature-independent switching capability, which considerably increases the flexibility of the heat management system in relation to a conventionally used wax thermostat. Owing to the combination of switched and non-switched inlets, the rotary slide valve itself can be kept simple in terms of construction and thus inexpensive and small in terms of structural size.
The configuration according to the invention offers the possibility of the heating circuit being shut off or throttled in temperature-independent fashion when no heating function is required. Owing to the reduced heat output and the reduced flow resistance for the coolant as a result of the omission of the heating circuit from the flow path, fuel consumption is reduced.
Since the heating circuit can be addressed separately, it is also possible for the flow conditions therein to be selected such that an improved supply with heat is achieved, for example by way of an increased volume flow through the heating heat exchanger, with altogether lower energy consumption.
In general, a rotary slide valve switches considerably more quickly than a thermostat valve. This makes it possible for the internal combustion engine, in the part-load range, in which the main cooler circuit is not open or is open only with a throttling action, to be operated warmer, that is to say with a higher coolant temperature, than before, because sudden increases in load and thus temperature in the engine region can, by adjustment of the rotary slide valve, be responded to quickly enough to keep the coolant temperature in the optimum range. For this purpose, it is for example possible for the heating circuit to be briefly shut off in targeted fashion in order to increase a volume flow through the main cooler circuit.
On the other hand, the heating circuit may also be used to reduce a volume flow through the engine cooling circuit, for example by virtue of a bypass return line from the engine cooling circuit to the rotary slide valve being shut off or throttled, and thus only a much smaller volume flow being moved through the heating circuit. Throttling of the flow through the engine cooling circuit ensures uniform and nevertheless reduced cooling of the internal combustion engine, such that the latter reaches its optimum operating temperature more quickly in the event of a cold start.
Here, the engine cooling circuit forms the so-called “small cooling circuit”, in which flow passes substantially only through the engine region, for example the cylinder head housing and the crankcase, but not through the air-cooled main cooler of the vehicle.
It is also possible for the flow through the engine cooling circuit or through the crankcase to be throttled in order to increase the heating action.
The outlet of the rotary slide valve preferably leads directly into the engine cooling circuit inlet, and is of non-switched design.
The coolant pump is for example arranged downstream of the outlet of the rotary slide valve and inward, in terms of flow, of the inlet of the engine cooling circuit into the engine region, in or in the immediate vicinity of an engine block of the internal combustion engine.
The return line of the main cooler circuit and/or a return line of the engine cooling circuit preferably issue(s) into in each case one switched inlet of the rotary slide valve. By way of the switchable return of the engine cooling circuit into the rotary slide valve, it is possible for a bypass (formed for example by the small cooling circuit) to be realized in a simple manner.
The rotary slide valve is advantageously arranged close to the engine in order to keep the flow paths, for example in the small cooling circuit, short. In the case of relatively short engines, for example a four-cylinder in-line engine, it is possible for the rotary slide valve to be positioned on the end side of the engine block, preferably in the immediate vicinity of the coolant pump that is optionally integrated into the engine block. By contrast, in the case of relatively long engines, for example a six-cylinder in-line engine, it is often advantageous, for space reasons, for the rotary slide valve to be arranged on the long side of the engine block.
A transmission oil cooling circuit having a transmission oil heat exchanger is normally provided. The return line thereof preferably issues into a non-switched inlet of the rotary slide valve. The transmission oil cooling circuit makes do with relatively inert temperature regulation, such that it is possible for a dedicated thermostat valve to be provided in the transmission oil cooling circuit, said dedicated thermostat valve being designed in particular as a conventional wax thermostat. In this way, the transmission oil cooling circuit can be configured in parallel with respect to the other cooling circuits, and can be coupled to the other cooling circuits, in particular to the engine cooling circuit, by way of the rotary slide valve. The transmission oil cooling circuit is switched in autonomous fashion by way of its dedicated thermostat valve. In this way, a control position of the rotary slide valve can be omitted.
The transmission oil cooling circuit is preferably decoupled from the other cooling circuits and may, in the warm-up phase, be shut off by way of the oil-side regulation in order to prevent heating of the coolant in the transmission oil cooling circuit, and thus assist the warm-up of the internal combustion engine.
An engine shut-off valve is preferably provided which can, for example, shut off a coolant feed line to the internal combustion engine downstream of the coolant pump.
In a warm-up phase, it is possible for all of the switchable inlets of the rotary slide valve to be closed, and thus for a flow through the engine cooling circuit to also be substantially throttled.
Here, the engine shut-off valve is preferably also closed, because this assists in preventing cavitation on the suction side of the coolant pump.
In the cooling circuits, there is normally provided a coolant expansion tank which can accommodate a certain volume of coolant and by which air can flow out to the surroundings.
The expansion tank is preferably connected to a non-switched inlet of the rotary slide valve.
In another possible embodiment, the expansion tank is connected to a switched inlet of the rotary slide valve. This makes it possible, for example during a cold start of the internal combustion engine, to prevent coolant circulation through the expansion tank, such that the coolant volume stored therein is not heated and said amount of heat is available for faster warm-up of the internal combustion engine. The coolant pump is preferably mechanically driven, wherein the drive is coupled to the internal combustion engine. It would however also be possible for an electrically driven main coolant pump to be used.
In the case of a mechanically driven coolant pump being used, it is advantageous for an additional electric coolant pump to be provided which permits a coolant movement through the coolant circuits even when the internal combustion engine is at a standstill, for example after an end of operation.
It is possible for the additional coolant pump to be arranged in an exhaust-gas turbocharger cooling circuit. This may be connected to the other cooling circuits via a non-switched inlet of the rotary slide valve. In another embodiment, the exhaust-gas turbocharger cooling circuit issues into the main return line of the engine cooling circuit.
The exhaust-gas turbocharger cooling circuit is preferably not controlled by way of the rotary slide valve if, in the afterrun situations after the operation of the internal combustion engine, it is necessary for the coolant movement in all of the cooling circuits through which flow must still pass to be effected by said exhaust-gas turbocharger cooling circuit by way of its additional coolant pump, and said exhaust-gas turbocharger cooling circuit may thus always be open.
It is however also possible for the additional coolant pump to be actuated in targeted fashion in order to conduct coolant into particular circuits by way of particular positions of the rotary slide valve. For example, it is possible for the rotary slide valve to be switched such that warm coolant is conducted by way of the additional coolant pump into the heating circuit in order to increase the heating power, for example in the case of the internal combustion engine being switched off in the context of an automatic start-stop system (MSA) or for other reasons.
A control unit and temperature sensors are preferably provided in the individual coolant circuits, and the rotary slide valve can preferably be switched by way of the control unit in a manner dependent on data determined by the temperature sensors.
The heat management system preferably has characteristic map-based control, in which specific data for the respective positions of the rotary slide valve in particular operating ranges are stored in the control unit. It is also possible for other vehicle data to be incorporated into the control of the rotary slide valve, for example a selected driving style, the present or desired fuel consumption, a position predictable via GPS, the outside temperature, or the presently engaged gear.
The invention will be described in more detail below on the basis of two exemplary embodiments and with reference to the appended drawings, in which:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.